"Come of age" is a phrase used to describe the transition from childhood to adulthood. The antonyms for this phrase are "stay young," "remain immature," and "settle for mediocrity." These words describe an individual who has not experienced personal growth or has not taken the necessary steps to mature and develop. Those who stay young do not embrace responsibility or take on new challenges. Remaining immature means that one has not developed emotionally or mentally. Settling for mediocrity suggests a lack of ambition or drive to achieve greatness. In contrast, those who come of age embrace adulthood with determination, ambition, and a desire for personal growth and development.